Study On Co-Metabolic Degradation Of4-Chlorophenol In Wastewater By Photosynthetic Bacteria

In this paper, photosynthetic bacteria PSB-DR with high degradation efficiency for4-chlorophenol (4-CP) was obtained by acclimation of gradual increase of4-CP concentration in the medium and multiplication, and their cells morphological and some physiological biochemical characteristics were identified. In order to provide theoretical basis for the application of photosynthetic bacteria (PSB) in chlorophenols containing wastewater treatment, the biodegradation characteristics of PSB-DR for simulated4-CP containing wastewater were investigated.Under darkness-aerobic condition, the PSB-DR growth and biodegradation characterizations of4-CP by PSB-DR at different carbon source, carbon source concentrations, initial pH, rotation speed, temperature and NaCl concentration were investigated. The optimal condition was as follows:glucose3g/L, pH7.5,135rpm, and30℃, respectively, and98.31%of4-CP (50mg/L) was removed after6days. Meanwhile, the kinetics of biodegradation was in accordance with the Haldane’s equation. And the kinetic constants obtained were rmax=0.14d-1, Km=33.91mg/L, and Ki=159.59mg/L. Moreover, the study about conexistence of4-CP and phenol,4-CP and2,4-dichlorophenol (2,4-DCP) were carried out under darkness-aerobic condition. When phenol concentration was100mg/L, the biodegradation rate of4-CP was90.24%which was the maximum. While the biodegradation rate of4-CP always decreased with the increased of2,4-DCP concentration.Under light-anaerobic condition, the PSB-DR growth and biodegradation characterizations of4-CP by PSB-DR at different carbon source, carbon source concentrations, initial pH, illumination, temperature and NaCl concentration were investigated. The optimal condition was as follows:sodium acetate3g/L, pH7.0,3094lx and30℃, respectively, and93.02%of4-CP (50mg/L) was removed after9days. Meanwhile, the kinetics of biodegradation was in accordance with the Haldane’s equation. And the kinetic constants obtained were rmax=0.08d-1, Km=44.9mg/L, and Ki=207.4mg/L. Moreover, biodegradation of simulated4-CP containing wastewater was scaled-up at a2-L home-made bioreactor under light-anaerobic condition. For the10-day HRT, the biodegradation rate of4-CP were100%,74.05%, and33.80%at the initial4-CP concentrations of20,50and100mg/L, respectively. On the basis of the experiment datas and previous reports, the possible biodegradation pathway was investigated,4-CP was dechlorinated to phenol, further converted to low toxic organic compounds and eventually degraded to CO2and methane under light-anaerobic condition.